The present invention relates to compositions for melting ice on surfaces such as streets, parking lots, sidewalks, etc. Such compositions are generally known, see for example, U.S. Pat. No. 2,988,509. Generally, and by way of example, these compositions commonly include monovalent and divalent chlorides, particularly of potassium, sodium, magnesium, and calcium. They are used in the maintenance of icy road surfaces and sidewalks during the winter. The combined use of sodium chloride and calcium chloride provides a composition which is effective at substantially lower temperatures and acts more rapidly to melt ice.
Use of a combination of sodium chloride and calcium chloride for deicing has existed since at least as early as the above referenced patent. However, one problem with these compositions is integrity of the composition during formation, storage, and use. For example, during use, the homogeniety of the composition, i.e. whether the sodium chloride settles away from the calcium chloride, as well as how fast the composition "melts" when exposed to snow and ice can both drastically affect the overall effectiveness of the composition. If, for example, individual particulate material of the composition becomes "fused" as it is exposed to snow and ice, the overall surface area is decreased and consequently, the effectiveness, in terms of rapidly melting the snow and ice is decreased. In short, if the particles are uniform, if they have a low bulk density, and if they are highly porous so that they are free flowing to maintain product integrity during storage, yet are also easily subject to fracture upon use, the most successful road and sidewalk deicing use will be achieved.
Much effort without success has been expended by those in the art in order to achieve a product which is, at the same time, stable during storage, free flowing, and yet which will also easily fracture to expose more surface and cause rapid melting of snow and ice during application.
It is a primary objective of the present invention to prepare uniform particles, substantially spherical in nature, which are highly porous, which have good product stability in packing, storage, and shipment, while also being easily subject to fracture, and therefore, disintegrate, and/or dissolve during use to allow rapid melting of snow and ice.
It is another primary objective of the present invention to provide the above composition by a method which involves pan agglomerating of deicer composition.
It is a further objective of the present invention to provide a composition which contains substantial amounts of sodium chloride and calcium chloride, which is made by pan agglomeration with a pan agglomerating fluid comprising mostly of a solution of magnesium chloride.
It is a further objective of the present invention to provide compositions of low bulk density, that are substantially spherical, highly porous particles, which provides for faster ice and snow melt than heretofore achievable.
It is a yet further process objective of the present invention to provide a process which is highly economical to perform, and which provides a sodium chloride, calcium chloride composition with minor amounts of magnesium chloride present and all in a pan agglomerated form.
It is a still further objective of the present invention to provide product which is pan agglomerated and, because of the use of this method of agglomeration allows for process flexibility to vary the composition of the deicer mixture as desired from run to run.
The method and manner of accomplishing each of the above objectives will become apparent from the detailed description of the invention which follows.